A small change can mean the most precious words from your doctor’s lips – “nothing to worry about”. Or it can be an early sign of disaster.

Your body temperature fluctuates throughout the day, and at any one time, different body parts body will have different temperatures. But it is something to worry about if your average temperature goes up by even just a few degrees, and stays there.

As it happens, a few degrees is also all it takes to make for a very sick planet.

Risk to health is "the real bottom line"In a series of reports on climate change and health, published in the medical journal The Lancet just prior to the Intenational Conference on Climate Change in Copenhagen, which starts today, medical experts urged governments not to neglect public health in discussions.

World Health Organisation Director General Margaret Chan stated in The Lancet that “the real bottom line of climate change is its risk to human health and quality of life."

Chan pointed out that the health problems associated with climate change aren’t new; they are “already huge, largely concentrated in the developing world, and difficult to control.”

But on an increasingly feverish planet these crises will be more intense, more unpredictable and more uncontrollable:

More heatWe’re in for more hot days and heat waves. This is particularly bad news for urbanites, as heat waves are generally worst in cities, whose heat-retaining tarred and concrete surfaces, and heat-generating motor vehicles and industries turn them into urban "heat islands".

And heat kills. The 2003 heat wave in Europe, for example, one of the worst in 150 years, caused deaths in the tens of thousands – and showed that even the developed world is poorly equipped to deal with such events.

We should expect many more heat-related deaths, mainly through cardiovascular and respiratory disease, and mainly in the most vulnerable: the elderly and chronically ill.

More wild weatherGlobal warming isn’t just a matter of heat; rising temperatures are likely to trigger more and worse "extreme" weather events, like floods, droughts, storms and wildfires. In this wilder world, weather patterns will be less predictable, which means it’ll be harder to plan for disasters, stretching public health budgets to the limit.

In addition to physical injury and death, natural disasters have other negative health impacts. Flooding can cause drinking water contamination and the spread of diarrheal diseases like cholera. Respiratory infections may increase from crowding (as happens in disaster relief shelters); molds, which flourish in the damp left by floodwaters, may also cause respiratory symptoms.

Survivors of natural disasters have higher rates of psychiatric disorders like anxiety and depression, and behavioural disorders in children. Developing nations would be particularly vulnerable to rising waters, because many of their inhabitants live on flood plains and coastal plains.

Droughts mean less water for food production, which would lead to more malnutrition, with long-term health consequences - especially for children. Again, developing countries, whose food security is already threatened, would bear the brunt.

Water scarcity may force people to use poorer quality sources of water, resulting in an increased incidence of diarrheal diseases.

More diseaseAnimals that carry infectious diseases, like mosquitoes and rats, generally thrive in warm, moist climates. A warmer world could give them a boost, allowing them to spread from the tropics and subtropics, and low-lying areas, into more temperate zones and higher altitudes, carrying with them scourges like malaria, dengue fever, yellow fever and encephalitis.

They’d spread in time too – longer summers would prolong transmission seasons. One estimate suggests that 260 to 320 million more people could be at risk for malaria by 2080.

More dirty airThe impact of certain air pollutants, like tropospheric ozone (the “bad” ozone in the lower atmosphere), tends to be more severe at higher temperatures. Wildfires, set to increase in number, are associated with worsened respiratory symptoms, and acute attacks of asthma, bronchitis and chest pain.

Warmer winters may mean an earlier start to the grass pollen season, and raised levels of certain tree pollens. Rising levels of carbon dioxide, the main greenhouse gas, also appears to stimulate the release of allergenic pollens and spores in some plants. Hay fever sufferers should brace themselves for more frequent, persistent and severe attacks.

Towards a healthier planet

The medical experts’ report wasn’t unrelenting doom and gloom, however: they also stated that there are many promising, relatively inexpensive interventions available to governments, the cost of which would be offset by the enormous health benefits.

Some examples cited in The Lancet:

If the third world swops polluting biomass (i.e. wood) stoves for lower-emission stoves, not only would millions of tonnes of CO2 be kept out of the atmosphere, but it would reduce the toxic fumes and particles that worsen respiratory disease and raise risk for lung cancer.

Persuading people to eat less meat would lower production in livestock-rearing economies, which make a hefty contribution to global warming and deforestation. This would also help fight heart disease, by cutting the amount of saturated animal fats in diets.

Planning urban areas to encourage walking and cycling would benefit health more than introducing low-emission vehicles. Medical scientists predict that less motorised transport and more alternative transport would lower carbon emissions, and also heart attacks, strokes and dementia. Road accident injuries would also fall dramatically.

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The information on Health24 is for educational purposes only, and is not intended as medical advice, diagnosis or treatment. If you are experiencing symptoms or need health advice, please consult a healthcare professional. See additional information.